Comments:
Scenario 13:
My allies have carryover gold, too.
This is another incentive to finish scenario 12 as fast as possible.
The enemy leaders are sitting ducks!
If surrounded in their keep they should attack (at least the ranged units).
The Bandit didn't try to heal the poison (in the previous win).

This scenario is perfectly playable with only level 1 units.
But I suggest using some veterans to finish earlier.
Your carryover gold should be about the same (more upkeep is offset by less turns used) but your allies will have more in the next scenario which may mean the difference between life and death.
My attached restart yielded them 14 and 13 more gold than in the previous win.

feels like 6/10 difficulty rate, and "6" is b/c of frozen terrain. Very easy map compared to previous one, that's good. (But probably I managed to get extra starting gold b/c I cheated in the prev scenario)

(1) What difficulty level and version of Wesnoth have you played the scenario on?
Nightmare 1.12.4

(2) How difficult did you find the scenario? (1-10)
6
258 starting gold

(3) How clear did you find the scenario objectives?
Clear

(4) How clear and interesting did you find the dialog and storyline of the scenario?
Clear

(5) What were your major challenges in meeting the objectives of the scenario?
Keeping the allied leaders alive, I guess. I sent my main squad through the east mountains while using a few other units to hold off the enemy in the west. In retrospect I should have recruited a strong unit and taken advantage of the frozen forest terrain which is advantageous against dwarves.
I used lots of assassins here, partially because I hadn't used them much so far and partially because marksman+poison is good in mountains. Trolls are good at taking hits, as always.

(6) How fun do you think the scenario is? (1-10)
7

(7) What, if any, are changes you would have made to the scenario to make it more fun?
dunno

(8) Was there any event that caused you to lose the game and forced you to reload or restart the scenario?
No